1. Field of the Invention
The present invention relates to a reactor comprised of a coil and a core placed in a container, and a method of producing the reactor for use in an electric power conversion device and the like.
2. Description of the Related Art
There is a known conventional reactor comprised of a coil and a core placed in a container. Japanese patent laid open publication No. JP 2006-004957 has disclosed such a conventional reactor comprised of a coil, a core placed in a container. The coil is spirally wound, and generates a magnetic flux when a current flows therein. The core is made of a resin mixture of magnetic powder and resin. The outer periphery side and the inner side of the coil in the container are filled with the resin mixture, in other words, the coil is embedded in the resin mixture placed in the container.
In the method of producing the reactor, at first, a conductive wire is spirally wound in a concentric configuration in order to make the coil.
Next, the coil is placed in the container, and then filled with the resin mixture. Finally, the resin mixture is solidified to make the core in which the coil is embedded. This completes the method of producing the reactor.
However, the conventional reactor has a following drawback. Because the conductive wire is made of copper, that is, the coil is made of copper, the coil is thermally expanded when a current flows therein. The thermal expansion of the coil generates pressure. The stress generated in the coil is applied to the core formed around the coil. That is, an excess stress is applied to the core when the coil is thermally expanded. This often causes that the core breaks, and a crack is generated in the reactor. This makes it impossible to provide a predetermined magnitude of inductance of the reactor.
In general, a high elastic modulus of the core often causes a crack therein. This means that the magnetic powder in the resin mixture forming the core has a high elastic modulus. One possible countermeasure to decrease the elastic modulus of the core is to decrease the amount of magnetic powder in the resin mixture in the core. However, this can decrease the magnetic characteristics of the core, and thereby makes it difficult to generate a desired amount of magnetic flux.